Question: Fluffy gravel

My new additions are still pooping gravel, poor things! but it gets a strange 'fluffy' coating around it. I'm just wondering if it is normal or not? I don't know how else to describe it really, it's a translucent white coating that kind of looks a bit fluffy as I've already said. When I got my first axie last year she pooped out a fair bit of gravel at the start but I don't remember seeing this coating on it.

The smallest guy as well has a constant kink in the very end of his tail but I can't figure out what could be stressing him, the water seems fine, although I am relying on nasty test strips at the moment until I'm paid at the end of the month but they are indicating that it is currently OK so I don't think it is too far out? They are the same as Scylla's and she is fine and dandy, the temp is a steady 20°C as well.

The two of them are in quarantine together but Jake seems fine and they seem to give each other plenty of space, Hoshi prefers to sit under the filter and Jake hides behind the 'forest' I've put in. Neither of them like going in the hide though, they sit on it instead... Also, I'm feeding them all on Dillies for the time being until I can get into the garden to go digging for earthworms and the new additions struggle to latch on to the fish, eventually manage to eat one and then get fed up with any other attempts and swim away :/ no good when I'm trying to fatten them up!

Didn't intend for it to be as long as it is! Then figured anything that doesn't seem normal compared to my healthy madam should probably be added in case it all points to something bad. Just to save confusion - Hoshi is the very small guy/gal, Jake is the one with the extra leg and I will have had Scylla a year in about 3 weeks

the fluffy stuff your talking about is only on the gravel the axolotl's poo'd out right? I'm not sure if you've left food out in the tank too long, but it usually gets fungus looking growths on it from rotting. Maybe the fluffy stuff is just the junk from your axolotl that's rotting, and it's stuck to the gravel? Rotting food usually looks kind of fluffy after a while.
My axololt's usually don't go in their hides either. I have pvc pipe, and a few aquarium hides and they just seem to ignore them, or perch on them. Ours probably just prefer the plants to the hides.

Yep it's only on the gravel that they have passed. I'm currently having to clean their tank once or twice a day even though they aren't eating much so the gravel seems to be coming out of them like that.
Any idea what might cause the kink in the little one's tail? Don't like the idea of him being stressed out

If the kink is at the end of the tail it could be a sign of stress, he most likely has a belly full of gravel and that is why he is upset. He might need a little holiday in the fridge to help relax and pass all the gravel.